Which schema file is required by OpenLDAP?

`inetorgperson.schema` is commonly used for representing people but is not strictly required for OpenLDAP to function; it's an extension.

The `core.schema` file defines the most basic and essential object classes (like `top`, `organizationalUnit`) and attributes (like `cn`, `sn`, `objectClass`) that are fundamental to any LDAP directory. It is implicitly or explicitly required for a functional OpenLDAP server.

There is no standard `openldap.schema` file that is a core requirement; the OpenLDAP project provides many standard and optional schemas.

`cosine.schema` provides many common object classes and attributes and is often included, but `core.schema` is more fundamental.

`misc.schema` contains miscellaneous object classes and attributes and is optional, not a core requirement.